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Rally - FMF Powerbomb/Megabomb or not?

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Posted (edited)

They provide performance gains, especially when other mods are done.  When I raced a fellow on a similar bike with a stock motor, I literally walked away from him on the highway from a dead stop, and got to our destination minutes before he did.  He was quite interested in what I had done to my bike to make it so much quicker than his.  I assumed he was also riding his as hard as I was, but he may not have been twisting the throttle as hard as I was. :)  I also noticed a ~10mph increase in my top speed and easy cruise speeds, which was important to be able to ride the bike on local Interstate highways with 70mph speed limits (so 80mph cars).  I can keep up with and pass average traffic now.

I am of the belief that these little Honda motors are designed to spin at high-rpm for an extended period of time.  So that's how I ride it when I am trying to go fast.  At the same time, it has enough torque now, to not have to spin it so hard on single track.

My performance mods consist of: 

  1. EJK (1.5, 2.5, 4.5, & stock switch points) (richened up the lean mixture quite a bit, but suffered in MPG down to 50-55mpg now)
  2. FMF PC4 & Megabomb (opened up the breathing and reduced weight)
  3. 13/40 gearing & SpeedoDRD correction (quicker response and more realistic gearing) 
  4. 2" airbox snorkle mod (potentially opened up breathing a bit.)
  5. K&N filter (potentially opened up breathing a bit)

That's it & relatively simple to bolt on.

There are other options you can go with for power gains, that cost less (CBR TB & PCM) or (CBR motor swap), or more with big bore kit & cam rebuild.

Have fun,

Doug

Edited by rz_racer_69

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I have the same mods except 13/42 gearing and removal of the judder spring in the clutch. All very worth it. Also did RaceTech gold valves and spring in front and a Hyperpro shock in back. Also very worth it.

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Yes! Suspension is very lacking. If you plan to do too much difficult offroading, you will find yourself bottoming the stock forks often. (unless you weigh 110 lbs)

At 190lbs, I have my rear spring tightened to max and can still load the bike down with 70lbs of camping gear and tools. 

I just slow down for the bumps! ?

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Non rally version here. Biggest thing I noticed when I did stage 1 mods is that high rpm power just wants to keep going and going. Stock has a noticable power loss after 8k rpm. Acceleration across the board is better as well.

I was running 13/42 before the stage 1 mod and went to 14/42 after. Slight lack vs 13/42 off road but almost comparable so i must have gained some performance gains. 14/42 would almost stall out before on one hill climb I like to do. Runs right up it now with stage 1 but it is not as good as it was on 13/42 and stock. Haven't tried stage 1 with 13/42 yet. I am doing more street riding lately so I wanted to bring the rpms down a bit for more speed.

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